We describe Pantheia, a system that constructs virtual models of real spaces from collections of images, through the use of visual markers that guide and constrain model construction. To create a model users simply `mark up’ the real world scene by placing pre-printed markers that describe scene elements or impose semantic constraints. Users then collect still images or video of the scene. From this input, Pantheia automatically and quickly produces a model. The Pantheia system was used to produce models of two rooms that demonstrate the eectiveness of the approach.